1. Field of the Invention
The present invention relates to an improvement in a torque converter comprising: a pump impeller connected to an input shaft; a turbine impeller which is mounted to oppose the pump impeller and to which a turbine shaft is connected; and a side cover integrally connected to the pump impeller to cover the turbine impeller; a radial bearing for concentrically retaining a hub of the side cover and the turbine shaft as well as a one-way clutch being disposed adjacent each other between the hub of the side cover and the turbine shaft extending through the hub, the one-way clutch being adapted to connect the turbine shaft and the side cover to each other when a reverse load is applied to the turbine shaft; a hub of an output gear being coupled to an outer end of the turbine shaft; a sealing means being mounted between the hubs of the output gear and the side cover.
2. Description of the Related Art
Such a torque converter is already known, as is disclosed in Japanese Patent Application Laid-open No. 2001-241530.
In such torque converter, when a reverse load is transmitted from the output gear to the turbine shaft during deceleration of a vehicle, the one-way clutch connects the turbine shaft and the side cover directly to each other. Therefore, the reverse load is transmitted from the turbine shaft directly to the side cover, and further from the pump impeller to a crankshaft, whereby a good engine brake effect can be obtained without occurrence of a slipping between the turbine impeller and the pump impeller. Moreover, the radial bearing adjoining the one-way clutch is interposed between the turbine shaft and the hub of the side cover to ensure the concentricity between them. Therefore, loads received by clutch elements such as sprags of the one-way clutch between the turbine shaft and the side cover can be equalized, thereby improving durability of the clutch. In addition, a working oil within the torque converter can be prevented by the sealing means from being leaked from an inner peripheral surface of the hub of the side cover.
In the conventionally known torque converter, the one-way clutch and the radial bearing are disposed on opposite sides of an annular projection formed at an intermediate portion of the inner peripheral surface of the hub of the side cover, and an outer race of the radial bearing is clamped axially by the annular projection and a retaining ring locked to the inner peripheral surface of the hub of the side cover in order to retain the bearing. Therefore, the formation of the inner peripheral surface of the hub of the side cover is obliged to be conducted from axially opposite ends of the hub due to the presence of the annular projection at the intermediate portion of the inner peripheral surface, and hence, the number of steps is larger, and it is difficult to reduce the cost.
Accordingly, it is an object of the present invention to provide a torque converter of the above-described type, wherein the entire inner peripheral surface of the hub of the side cover can be formed from the side of an inner end, whereby the retaining of the radial bearing can be conducted simply, while providing a reduction in the number of steps, and in turn a reduction in cost.
To achieve the above object, according to a first feature of the present invention, there is provided a torque converter comprising: a pump impeller connected to an input shaft; a turbine impeller which is mounted to oppose the pump impeller and to which a turbine shaft is connected; and a side cover integrally connected to the pump impeller to cover the turbine impeller; a radial bearing for concentrically retaining a hub of the side cover and the turbine shaft as well as a one-way clutch being disposed adjacent each other between the hub of the side cover and the turbine shaft extending through the hub, the one-way clutch being adapted to connect the turbine shaft and the side cover to each other when a reverse load is applied to the turbine shaft; a hub of an output gear being coupled to an outer end of the turbine shaft; a sealing means being mounted between the hubs of the output gear and the side cover, wherein an inner peripheral surface of the hub of the side cover is formed into a stepped configuration by a larger-diameter inner peripheral surface portion located on the side of its base end and a smaller-diameter inner peripheral surface portion located on the side of its tip end and connected to the larger-diameter inner peripheral surface portion through an annular step; an outer race of the radial bearing fitted to the larger-diameter inner peripheral surface portion being clamped axially by the annular step and a retaining ring locked to the larger-diameter inner peripheral surface portion; and the hub of the output gear is relatively rotatably fitted to the smaller-diameter inner peripheral surface portion with the sealing means mounted between their fitted surfaces.
With the first feature, the inner peripheral surface of the hub of the side cover is formed into the stepped configuration by the larger-diameter inner peripheral surface portion which is located on the side of its base end and on which the radial bearing and the one-way clutch are mounted, and the smaller-diameter inner peripheral surface portion located on the side of its tip end. Therefore, the entire stepped inner peripheral surface can be formed at a stroke, leading to a decrease in steps and a reduction in cost.
Moreover, the annular step between the larger-diameter inner peripheral surface portion and the smaller-diameter inner peripheral surface portion is utilized for axially retaining the outer race of the radial bearing and hence, the retaining structure is simple, and a further reduction in cost can be provided.
Furthermore, the first sealing means is mounted between the smaller-diameter inner peripheral surface portion and the hub of the output gear relatively rotatably fitted to the smaller-diameter inner peripheral surface portion, and hence, the diameter of the first sealing means can be reduced, and a load on the first sealing means can be alleviated, leading to an enhancement in durability thereof.
According to a second feature of the present invention, in addition to the first feature, the sealing means is comprised of an annular sealing groove defined in an outer peripheral surface of the hub of the output gear, and a seal ring mounted in the sealing groove to come into resilient close contact with the smaller-diameter inner peripheral surface portion, so that the force of close contact of the seal ring with the smaller-diameter inner peripheral surface portion is increased by a centrifugal force applied to the seal ring.
With the second feature, the force of close contact of the seal ring with the smaller-diameter inner peripheral surface portion is increased in accordance with an increase in rotational speeds of the hub of the side cover and the output gear, and it is possible to effectively prevent the leakage of an internal pressure rising during rotation of the torque converter at a high speed.
According to a third feature of the present invention, in addition to the second feature, the seal ring is comprised of a resilient ring member which has a single abutment and which is provided with such a radial tension that it has a diameter larger than that of the smaller-diameter inner peripheral surface portion in its free state, an end face of the seal ring facing the abutment being inclined with respect to an axis or a radius line of the ring.
With the third feature, the mounting of the hub of the output gear in the sealing groove can be conducted easily by widening the abutment and moreover, the force of close contact of the seal ring with the smaller-diameter inner peripheral surface portion can be increased reliably in accordance with increases in rotational speeds of the hub of the side cover and the output gear.
In addition, since the end face of the seal ring facing the abutment is inclined with respect to the axis or radius line of the ring, the leakage of a working oil from the abutment can be minimized.
According to a fourth feature of the present invention, in addition to any of the first to third features, the output gear is comprised of the hub fitted to the turbine shaft and to the hub of the side cover, an arm extending radially from an outer periphery of the hub at one end thereof, and a toothed rim extending axially to overhang from an outer peripheral end of the arm toward the side cover, so that an annular recess is defined between the rim and the hub, and wherein the outer peripheral surface of the hub of the side cover is comprised of a larger-diameter portion located on the side of its base end and having a diameter substantially equal to that of the annular recess, and a smaller-diameter portion located on the side of its tip end, the smaller-diameter portion being disposed in the annular recess, the larger-diameter portion being disposed outside the annular recess, a corner of the annular recess on the side of the rim being rounded.
With the fourth feature, the smaller-diameter portion of the hub of the side cover is disposed in the annular recess of the output gear and hence, the axial compactness of the torque converter can be achieved, while ensuring a sufficient width of the toothed rim.
Moreover, although the annular recess and the larger-diameter portion of the hub of the side c over are formed to have the substantially equal diameters, the rounded shape having a large curvature radius can be provided to the corner of the annular recess on the side of the rim without being interfered by the larger-diameter portion, and hence it is possible to avoid the concentration of a stress at the corner to contribute to an enhancement in durability of the output gear.
The hub of the side cover comprised of the larger-diameter portion on the side of its base end and the smaller-diameter portion on the side of its tip end has a rational wall thickness corresponding to a load, and thus a reduction in weight and strength can be satisfied.
According to a fifth feature of the present invention, in addition to the first feature, the turbine shaft is lightly press-fitted into the hub of the output gear, and their fitted faces are beam-welded to each other over the entire periphery at outer end faces of the hub and the turbine shaft.
With the fifth feature, the turbine shaft is lightly press-fitted into the hub of the output gear and hence, a relatively small load suffices for such press-fitting, and even if the hollow turbine shaft is not especially of a larger wall thickness, deformation of the turbine shaft due to the press-fitting can be minimized. Moreover, the lightly press-fitted portions are coupled firmly to each other over the entire periphery by the beam-weld zone and hence, the lack of the coupling strength of the turbine shaft and the output gear due to the light press-fitting can be sufficiently compensated for, and the sealing of the lightly press-fitted portions can be also achieved reliably. Furthermore, a relatively small heat input suffices for the beam welding and hence, the thermal deformation of various portions due to the heat input is excluded.
According to a sixth feature of the present invention, in addition to the fifth feature, an outer peripheral surface of the turbine shaft is formed with a larger-diameter portion located on the side of its base end, and a smaller-diameter portion connected to the larger-diameter portion through an annular step, and the one-way clutch is fitted to the larger-diameter portion, while an inner race of the radial bearing is fitted to the smaller-diameter portion and clamped axially by the annular step and the hub of the output gear fitted to the smaller-diameter portion.
With the sixth feature, the inner race of the radial bearing can be retained simply without use of a special retaining ring. Moreover, the depth of press-fitting between the hub of the output gear and the turbine shaft can be defined easily and correctly by putting the hub of the output gear into abutment against the annular step with the inner race of the radial ball bearing interposed therebetween.
According to a seventh feature of the present invention, in addition to the sixth feature, the annular step has a tapered face formed at its outer peripheral edge for guiding the fitting of the one-way clutch to the larger-diameter portion.
With the seventh feature, the one-way clutch can be mounted easily on the larger-diameter portion of the turbine shaft by the guiding function of the tapered face without being obstructed by the annular step, thereby contributing to an enhancement in assemblability.
According to an eighth feature of the present invention, in addition to the first feature, a stator impeller disposed between the pump impeller and the turbine impeller is made of a light alloy; an outer peripheral surface of a sleeve made of a steel is integrally coupled to an inner peripheral surface of a hub of the stator impeller; and a hollow stator shaft relatively rotatably carried on an outer periphery of an input shaft is spline-coupled to an inner periphery of the sleeve.
With the eighth feature, the weight of the stator impeller can be reduced by forming it from the light alloy, and the durability of coupled portions of the stator impeller and stator shaft can be enhanced by spline-coupling the stator shaft to the sleeve made of the steel.
According to a ninth feature of the present invention, in addition to the eighth feature, the sleeve is press-fitted to the inner peripheral surface of the hub.
With the ninth feature, the sleeve can be thermally treated independently before being press-fitted into the hub, and thus a desired durability can be provided easily to the sleeve irrespective of casting of the stator impeller.
According to a tenth feature of the present invention, in addition to the ninth feature, the hub of the stator impeller has a smaller-diameter inner peripheral surface portion and a larger-diameter inner peripheral surface portion formed thereon with a central partition wall interposed therebetween; the sleeve is press-fitted to the smaller-diameter inner peripheral surface portion; one side of an inner race of a ball bearing for supporting the turbine impeller on the outer periphery of the stator shaft is put into abutment against an outer end face of the sleeve; a portion of the hub of the pump impeller is disposed within the larger-diameter inner peripheral surface portion; a thrust bearing having a thrust plate is interposed between the hub and the partition wall with the thrust plate put into abutment against the partition wall; and the axial position of the stator impeller is defined by the ball bearing and the thrust bearing.
With the tenth feature, a thrust load generated on the stator impeller is supported by the ball bearing through the sleeve made of the steel and by the thrust plate of the thrust bearing through the partition wall, whereby the durability of the hub made of the light alloy against the thrust load can be enhanced. In addition, since a portion of the hub of the pump impeller is disposed along with the thrust bearing within the larger-diameter inner peripheral surface portion of the hub of the stator impeller, the amount of outward protrusion of the hub can be decreased to contribute to the compactness of the torque converter.
According to an eleventh feature of the present invention, in addition to the tenth feature, the inner race of the ball bearing is formed to have a wall thickness larger than that of an outer race of the ball bearing, so that an area of abutment of the inner race against the sleeve is increased.
With the eleventh feature, the area of abutment of the inner race against the sleeve can be increased by forming only the inner race of the ball bearing with the large wall thickness, while minimizing an increase in diameter of the ball bearing, whereby the surface pressure on the inner race and the sleeve can be decreased, leading to an enhancement in durability.
According to a twelfth feature of the present invention, in addition to the first feature, a pair of radial needle bearings are interposed between a stator shaft connected to a stator impeller disposed between the pump impeller and the turbine impeller as well as an input shaft extending through the stator shaft, and support opposite ends of the stator shaft for rotation; a freewheel is interposed between an outer tube formed at an outer end of the stator shaft and an inner tube relatively rotatably supported on the input shaft and non-rotatably supported on a stationary structure and disposed concentrically within the outer tube; a radial needle bearing is interposed between the input shaft and the inner tube, the radial needle bearing being located adjacent the radial needle bearing located at the outer end of the stator shaft and comprising a needle roller having a diameter larger than that of the radial needle bearing located at the outer end of the stator shaft.
With the twelfth feature, the radial needle bearing on the inner tube and the radial needle bearing at the outer end of the stator shaft cannot enter the bearing housing of the other because of a difference between the diameters of the needle rollers and thus, a reduction in durability thereof due to the mutual interference can be prevented. Moreover, since the needle roller of the radial needle bearing on the inner tube has the diameter larger than that of the radial needle bearing at the outer end of the stator shaft, the durability of the radial needle bearing on the inner tube can be enhanced further and hence, can endure the high relative rotation between the input shaft and the inner tube sufficiently.
According to a thirteenth feature of the present invention, in addition to the twelfth feature, a flat washer is interposed between both the radial needle bearings adjoining each other.
With the thirteenth feature, the interference between the radial needle bearings adjoining each other can be prevented more reliably by the flat washer.
According to a fourteenth feature of the present invention, in addition to the first feature, a circulation circuit for a working oil is defined by the pump impeller, the turbine impeller and a stator impeller disposed between the pump impeller and the turbine impeller; a stator shaft rotatably supported on the input shaft through first and second inner periphery-side radial bearings arranged axially is connected at its inner end to the stator impeller; the turbine shaft is rotatably supported on the stator shaft with an outer-periphery side radial bearing interposed therebetween; a freewheel is interposed between an outer end of the stator shaft and a stationary structure; the input shaft is provided with an inlet bore for permitting the working oil to flow into the circulation circuit and an outlet bore for permitting the working oil to flow out of the circulation circuit; an inner end of the outer-periphery side radial bearing is in communication with the circulation circuit; and a sealing means is provided between opposed peripheral surfaces of the turbine shaft and the stator shaft axially outside the outer-periphery side radial bearing.
With the fourteenth feature, the outer-periphery side radial bearing can be lubricated by the working oil in the circulation circuit, and the leakage of the oil from the outer-periphery side radial bearing to the outside can be prevented by the sealing means. Therefore, even if the capacity of an oil pump for supplying the working oil to the circulation circuit C is not particularly increased, the lack of the amount of the working oil supplied to the circulation circuit cannot be brought about, and the torque converter can exhibit a desired transmitting performance.
According to a fifteenth feature of the present invention, in addition to the fourteenth feature, the inlet bore is brought into communication with the circulation circuit through the first inner periphery-side radial bearing at the inner end of the stator shaft, and an annular oil sump and a pair of annular constrictions axially sandwiching the annular oil sump are provided between the first and second inner periphery-side radial bearings and between opposed peripheral surfaces of the input shaft and the stator shaft, the annular oil sump being in communication with the outer-periphery side radial bearing through a transverse bore provided in the stator shaft.
With the fifteenth feature, the working oil can lubricate the first inner periphery-side radial bearing in the middle of flowing from the inlet bore in the input shaft toward the circulation circuit, and a portion of the working oilcan be appropriately supplied through one of the annular constrictions adjoining the first inner periphery-side radial bearing. The working oil which has exited from the circulation circuit and has lubricated the outer-periphery side radial bearing can be appropriately supplied from the annular oil sump through the other annular constriction not only to the second inner periphery-side radial bearing but also to the freewheel to lubricate them.
The above and other objects, features and advantages of the invention will become apparent from the following description of the preferred embodiment taken in conjunction with the accompanying drawings.